Field of the Invention
The present invention relates to an image forming apparatus such as a copier, a printer, a facsimile machine, a multi-function printer having multiple functions of these devices.
Description of the Related Art
Hitherto, there has been known an image forming apparatus of an intermediate transfer type configured to primarily transfer a toner image formed on a photosensitive drum to an intermediate transfer belt serving as an image bearing member and to secondarily transfer the toner image from the intermediate transfer belt to a recording medium. A transfer roller, i.e., a secondary transfer outer roller, configured to come into contact with an outer circumferential surface of the intermediate transfer belt is disposed in a secondary transfer portion where the toner image is secondarily transferred onto the recording medium and where the secondary transfer is performed a transfer voltage applied to the transfer roller.
The transfer roller is provided with an elastic layer around a conductive shaft portion and conductivity is imparted to the elastic layer by a conducting agent such as an ion conducting agent dispersed in the elastic layer. Accordingly, if an application time of voltage applied to the transfer roller increases depending on its use, ion within the ion conducting agent is apt to be polarized so as to be biased to either one side of a roller surface side or a shaft portion side, resulting in an increase of electric resistance caused by the polarization. Then, in order to suppress the increase of the electric resistance caused by the polarization, Japanese Patent Application Laid-open No. 2005-316200 proposes an image forming apparatus configured such that voltage is applied from a power feeding roller serving as a power feeding rotary member being in contact with a surface of the transfer roller to the transfer roller and to transfer the toner image from the intermediate transfer belt to the recording medium.
However, in a case where toner adheres to the transfer roller from the intermediate transfer belt to the transfer roller concerning the transfer roller disclosed in Japanese Patent Application Laid-open No. 2005-316200, the toner may adhere also to the power feeding roller being in contact with the transfer roller. If the toner adheres on the power feeding roller, irregularity of electric current flowing from the power feeding roller to the transfer roller may occur. Still further, the toner adhering on the power feeding roller may adhere again to the transfer roller, possibly contaminating a back surface of the recording medium.
Accordingly, the present disclosure provides an image forming apparatus including the power feeding rotary member capable of restraining a defective image caused by the toner adhering on the power feeding rotary member.